In order to observe an inner structure in a minute region of a substance, a scanning transmission electron microscope (STEM), a transmission electron microscope (TEM), or the like is used. As a typical observation method of observing the inside of a sample by using such an electron microscope, a method has been known in which a sample that is sliced into such a thickness that an electron beam can be transmitted therethrough is arranged on a meshed sample support with multiple pores and the transmitted electron beam is obtained by a detector that is arranged on a side opposite to an electron source side with respect to a sample surface. However, since the method employs a configuration in which the sample floats over pores of the mesh, it is significantly difficult to perform an operation of mounting the sample on the sample support. Thus, PTL 1 proposes an electron detector on which a sample to be observed is directly placed.
In addition, a minute region of a substance can also be observed by an optical microscope as well as the electron microscope. By using the optical microscope, it is possible to obtain color information that cannot be obtained by the electron microscope in principle. According to the optical microscope, it is possible to obtain a transmission optical image by irradiating a sample with white light or specific light and forming an image from light which is absorbed by or emitted from the sample and has color information. In doing so, it is possible to dye only a specific region in a sample, such as biological cells, by applying a specific coloring material to the cells and to thereby observe which region has been dyed or has not been dyed by observing the color. This method has been widely used in the fields of pathologic diagnosis and life sciences, in particular.
While the electron microscope cannot obtain color information, the electron microscope can observe a minute region, which cannot be observed by the optical microscope, with high resolution. In addition, information that can be obtained from an image of the electron microscope is information reflecting differences in density of the sample and is different from information that can be obtained by the optical microscope.